Clutch Disc Service
In most cases, the clutch disc is replaced when any
kind of clutch teardown is done, since it is relatively inex-
pensive. If the disc was recently replaced or appears to be
in excellent condition, it can be reused. Before deciding to
reuse the disc, it should be carefully checked.
Warning: Asbestos dust is harmful. Avoid
breathing any dust from the clutch disc, as
it can contain large amounts of cancer-
causing asbestos. Even new clutch discs often
contain some asbestos.
If you intend to reuse the clutch disc, do not wash it
in any kind of cleaning solvent. Solvent will ruin the clutch
disc friction facings.
Inspect the clutch disc for thin or cracked friction
material. The disc thickness can be checked with a slid-
ing caliper, as shown in Figure 7-28. Usually, however,
other indications will be obvious and this step will be
unnecessary. Check the disc for loose rivets, oil-soaked
friction facings, or broken cushion springs. Make sure the
hub flange splines are not worn and they slide freely on
the splines of the transmission input shaft. If the clutch
disc shows any wear or damage, it should be replaced.
Figure 7-29 shows various types of clutch disc damage
you might find during inspection, along with possible
reasons damage occurred.
If a replacement disc is to be used, it must be carefully
compared to the old one before it is installed. Many clutch
problems are caused by installing the wrong replacement
disc. It is especially important to check the hub flange size
against the old disc. A hub flange that is too large will
contact the flywheel and pressure plate, causing clutch
disc damage and gear clash. As a final check, slip the
replacement disc over the transmission input shaft to make
sure it has the correct splines.
Pressure Plate Assembly Service
The pressure plate assembly is another clutch compo-
nent that is almost always replaced when the clutch is
repaired. You should spend a few moments checking the
pressure plate assembly. This will help you determine the
cause of the clutch problem and learn how it can be pre-
vented in the future.
Pressure plate assembly inspection
The pressure plate machined surface develops the
same problems as the flywheel surface. Check for wear,
scoring, signs of overheating, cracks, and warpage. The
pressure plate will usually show more heat damage than
the flywheel.
Retaining rivets for diaphragm-spring pivot rings
should be checked for looseness. Loose rivets indicate
long usage or rough clutch treatment.
Elongation of the bolt holes in the clutch cover is an
indication the clutch cover attaching bolts were loose. The
pressure plate assembly may bounce against the flywheel
if these bolts are loose, which would cause the holes to
elongate.
Check for weak pressure plate springs and for signs of
overheated springs. The release fingers or levers should be
checked for wear and misadjustment. If any fingers or levers
are lower than the others, the pressure plate application will
be uneven. The clutch may grab or chatter. Severe wear at
the contact point with the throwout bearing indicates the
clutch has seen much use or there was no free play.
Figure 7-30 shows various types of pressure plate assem-
bly damage you might find during inspection, along with
possible reasons the damage occurred. This damage may
range from chatter marks on the pressure plate to a scored
pressure plate or broken release levers. Being able to readily
identify the damage will result in better service times.
Chapter 7 Clutch Problems, Troubleshooting, and Service 145
Sliding
caliper
Measure clutch disc
thickness and compare
to specs
Sliding
caliper
Clutch disc
facing
A
B
Figure 7-28. Inspecting the clutch disc. A—Clutch disc thick-
ness can be measured with a sliding caliper. If thickness
specifications are available, the thickness can be compared
to determine whether the disc can be reused. B—Depth
gauge on sliding caliper or depth micrometer can be used to
determine the distance from the top of the clutch disc rivets
to the surface of the friction facing. If the rivets are too near
the surface, the disc is worn out and should be replaced.
(Honda, DaimlerChrysler)